Biomass and Carbon Sequestration Potential of Oxytenanthera abyssinica in the Homestead Agroforestry System of Tigray, Ethiopia

Oxytenanthera abyssinica forms an important constituent in the homestead agroforestry system of Tselemti district of Northern Ethiopia. Biomass and carbon sequestration potential of O. abyssinica in the land managed by farmers was studied from November to January 2013/14 in Serako kebele. Samples of six culms per age classes in three replications, 18 culms in total were harvested for biomass analysis. Allometric equations were then developed relating to leaf, branch and culm biomass with breast height diameter (DBH) and Age as independent variables. To evaluate the effect of Age and DBH on total biomass of O. abyssinica, 9 different treatments with three replications were used. In total, 27 culms were randomly selected for biomass and carbon stock determination based on the developed allometric equation. Samples were then collected from three levels of age, i.e. less than one year, one to three years and greater than three years at three DBH levels of 2.55 – 3.18 cm, 3.19 – 3.82 cm and 3.83 – 4.46 cm. Carbon fraction of O. abyssinica was determined using destructive ashing method by taking sample specimens both from the above ground and below ground biomass. Carbon stock was significantly higher in one to three and greater than three years than less than one year culm age (P<0.001). Older culms were capable to sequester more carbon than younger culms with 3.8, 3.9 and 3.5 kg culm-1for the three age classes respectively. O. abyssinica has a significant effect on climate change mitigation through carbon sequestration. Key - words: allometric equation, carbon sequestration, Oxytenanthera abyssinic

Woody Species Diversity in Oxytenanthera abyssinica Based Homestead Agroforestry Systems of Serako, Northern Ethiopia

In northern Ethiopia, establishment of exclosures and management of remnant protected natural forests to conserve and enhance forest products and services have been practiced for the past three decades. However, empirical data on the effectiveness of lowland bamboo based homestead agroforestry system in rescuing woody species diversity are lacking. The study was assessed the woody species diversity, density and composition of O. abyssinica based homestead agroforestry systems in Serako, Tselemti district. Data were collected from a total of ninety nine farms and plots with 10m*10m area, ninety from less than five year, five to ten years and greater than ten years domestication of O. abyssinica based homesteads and one exclosure with nine plots as comparison were taken. The study revealed that species density, richness and diversity were significantly higher in the exclosure than in the three homesteads (p<0.000). The study showed that a total of 48 tree species in 25 families and 24 tree species in 11 families for the homestead agroforestry systems and exclosure respectively were recorded. Following the age gradient, there was a significant difference in density, richness and diversity between greater than ten and less than five year domesticated O. abyssinica homestead agroforestry systems (p<0.000). This study confirmed that woody species diversity was higher for those households that domesticate O. abyssinica on their homesteads earlier than those households that domesticate later on their homesteads. Oxytenanthera abyssinica was not found in the exclosure, showing a distinct conscious selection for planting in the homesteads as agroforestry system. It is suggested that homestead agroforestry systems are effective for increasing biodiversity and socio-economic contributions to rural households. Keywords: Oxytenanthera abyssinica, woody species diversity, Tselemti

Effect of Soil and Water Conservation on Rehabilitation of Degraded Lands and Crop Productivity in Maego Watershed, North Ethiopia

Many soil and water conservation (SWC) measures were undertaken to decrease land degradation in Ethiopia. However, evaluation of their performance is essential to understand their success or failure and readjusting accordingly in the future planning. Therefore, the objective of this study was to evaluate effectiveness of SWC measures in rehabilitation of degraded watershed and increase crop productivity in Maego watershed, Ethiopia. Seventy six sample plots were randomly taken from treated and untreated sub-watersheds for woody species and soil sampling. Crops yield was measured on top side, middle zone and below side of SWC structures. There were significantly higher woody species density and diversity, total nitrogen (TN), soil organic matter (SOM) and soil moisture in the treated uncultivated land than the untreated one. The highest tree and sapling species density and diversity, TN and SOM were recorded on the exclosure part of the treated sub-watershed. Landscape position affected soil fertility, but has no effect on woody species density and diversity. The highest barley and wheat yield was measured on top side of SWC structures. Therefore, physical SWC structures should be integrated with exclosure to enhance rehabilitation of degraded watersheds/landscapes. Integration of biological SWC measures that improve soil fertility are essential on the cultivated land of the watershed. Most of the existing SWC structures, especially the old ones are filled with accumulated sediment, so maintenance is needed

Effect of soil and water conservation on rehabilitation of degraded lands and crop productivity in Maego watershed, North Ethiopia

Many soil and water conservation (SWC) measures were undertaken to decrease land degradation in Ethiopia. However, evaluation of their performance is essential to understand their success or failure and readjusting accordingly in the future planning.  Therefore, the objective of this study was to evaluate effectiveness of SWC measures in rehabilitation of degraded watershed and increase crop productivity in Maego watershed, Ethiopia. Seventy six sample plots were randomly taken from treated and untreated sub-watersheds for woody species and soil sampling. Crops yield was measured on top side, middle zone and below side of SWC structures. There were significantly higher woody species density and diversity, total nitrogen (TN), soil organic matter (SOM) and soil moisture in the treated uncultivated land than the untreated one. The highest tree and sapling species density and diversity, TN and SOM were recorded on the exclosure part of the treated sub-watershed. Landscape position affected soil fertility, but has no effect on woody species density and diversity. The highest barley and wheat yield was measured on top side of SWC structures. Therefore, physical SWC structures should be integrated with exclosure to enhance rehabilitation of degraded watersheds/landscapes. Integration of biological SWC measures that improve soil fertility are essential on the cultivated land of the watershed. Most of the existing SWC structures, especially the old ones are filled with accumulated sediment, so maintenance is needed